SiC (silicon carbide) is expected to be a material for next-generation semiconductor devices. SiC has excellent physical properties, having a band gap three times wider than that of Si (silicon), a breakdown field strength approximately 10 times higher than that of Si, and a heat conductivity approximately three times higher than that of Si. A semiconductor device that has low loss and is capable of high-temperature operation can be realized by taking advantage of those properties.
In a bipolar device such as a diode using SiC, the lifetime of minority carriers becomes shorter due to defects such as carbon vacancies. If the lifetime of minority carriers becomes shorter, the rate of decrease in reverse recovery current at a time when the device is turned off becomes higher, resulting in increased noise. This problem is particularly noticeable in cases when the lifetime of minority carriers in the vicinity of an electrode which is close to an edge of a depletion layer is short.
So as to reduce noise at a time when the device is turned off, there is a demand for a lower rate of decrease in reverse recovery current, and realization of soft recovery characteristics.